<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .aa{
            width: 30px;
            margin: 3px;
            border: 2px solid black;
            padding-bottom: 100px;
            padding: 10px;
            background-color: red;
        }
    </style>
</head>
<body>

<div class="aa" >
    你好
</div>
</body>
</html>